Electric lamp



y 7, 1968 G. LLOYD 3,382,403

ELECTRIC LAMP Filed July 20, 1965 INVENTOR. GORDON L L 0 YDWARREMBROSLER, CYPHEI? 8 ANGL/M 47' T ORA/E Y5 United States Patent O3,382,403 ELECTRIC LAMP Gordon Lloyd, 6906 Norfolk Road, Berkeley,Calif. 94705 Filed July 20, 1965, Ser. No. 473,347 6 Claims. (Cl.315-65) The invention relates to electric lamps and more particularly toconstructions thereof capable of indicating a failure of a lightemitting element.

There is a great need in many industries and for many applications foran electric light bulb which is absolutely reliable. Such bulbs are usedas indicators in a variety of apparatus and systems and failure of anindicator lamp can cause great loss of life and property when theindicator lamp which has failed is relied upon to indicate a conditionof a system, part of a system, or condition of a specific group ofcomponents. Such uses and applications are very widespread and almostlimitless. A few examples include control panels in aircraft, spacecraftand control towers; call lights for police, firemen, hospital personnel;trafiic lights; medical and hospital equipment, such as emergencygenerators, iron lungs, and other electrical or electronic equipment;indicator lamps showing condition of various equipment such as oil andgenerator warning lights in automobiles, ships or aircraft; andgenerally any lamp designed to indicate malfunction of any mechanical,electrical or electronic system where damage to equipment, personnel andproperty may occur.

An object of the present invention is to provide an electric indicatorlamp of the character described which has a very high order ofreliability and dependability and which will provide a visual signal tothe user or operator of the equipment with which the lamp is used of thefailure of the primary light emitting element of the lamp so thatimmediate replacement of the lamp may be effected.

Another object of the present invention is to provide an electric lampof the character described which can be manufactured in a completevariety of sizes and shapes and base designs used in currently availableindioat-or lamps; and which may be used to replace any existingindicator lamp currently in use directly and without modification of anycircuitry.

A further object of the present invention is to provide an electric lampof the character described which will alford a reduction of time spentin maintenance and repair of equipment in providing an immediateindication of lamp failures, location of failures indicated by lamps,and the prevention and minimizing of inconvenience to customers andpersonnel using apparatus equipped with the present lamps.

Still another object of the present invention is to provide an electriclamp of the character above which may be manufactured at smalladditional cost.

The invention possesses other objects and features of advantage, some ofwhich of the foregoing will be set forth in the following description ofthe preferred form of the invention which is illustrated in the drawingaccompanying and forming part of this specification. It is to beunderstood however, that variations in the showing made by the saiddrawing and description maybe adopted within the scope of the inventionas set forth in the claims.

Referring to said drawing:

FIGURE 1 is a side elevation of an electric lamp constructed inaccordance with the present invention.

FIGURE 2 is an enlarged fragmentary side elevation of portions of thelamp, the view being taken as indiiated by line 2-2 in FIGURE 3.

FIGURE 3 is a plan sectional view of the lamp taken substantially on theplane of line 3-3 of FIGURE 1.

1 FIGURE 4 is an electric schematic diagram of the amp.

FIGURE 5 is an electric schematic diagram of the lamp with the partsshown in a dilferent position.

FIGURE 6 is an electric schematic diagram of a modified form of thelamp.

FIGURE 7 is an electric schematic diagram of the lamp illustrated inFIGURE 6 but with parts in another position.

The electric lamp of the present invention comprises, briefly, primaryand secondary light emitting elements 11 and 12; a thermostaticallyoperated switch 13 mounted in position for heating by elements 11 and12; the elements and switch being connected for normal operation of theprimary element 11; and the switch being constructed to automaticallymove between heated and unheated positions and being connected to makeand break electrical connection to the secondary element 12 in itsunheated and heated positions respectively, whereby upon open circuitingof the primary element 11 the switch will produce periodic energizationand blinking or flashing of the secondary element 12.

As will be seen in FIGRE 1, the several elements of the lamp areenclosed in an envelope 14 which is secured to an appropriate electricalcontacting base 16, such as the threaded base here shown, although aswill be understood any lamp base may be used.

It will be further seen that the lamp has power input terminals 17 and18 which are carried by an internal stem 21 supported by base 16. Thelight emitting elements 11 and 12 are preferably composed of filamentsand as will be seen primary filament 11 has its ends here secured topower input terminals 17 and 18 so that the primary filament will beenergized whenever electric power is supplied to terminals 17 and 1-8.Secondary filament 12 has one end secured to a branch terminal 22secured to input terminal 17 and has its opposite end secured to a rigidsupporting electrical conductor 23 which is supported at its lower endin stem 21. An electric circuit is completed through secondary filament12 by switch 13 which is here connected to input terminal 18 and ismounted to provide in an unheated condition electric contact with aportion 24 of conductor 23. In the present construction switch 13 ispreferably composed of an electric current conducting bimetal armconnected at one end 26 to conductor 18 and having an opposite end 27mounted to swing away from and into electrical contact with portion 24of conductor 23 when the arm is heated and cooled respectively and shownin full and dashed lines in FIGURE 2.

As will be seen from FIGURES 1 and 3, filaments 11 and 12 are offsetfrom each other and the bimetal switch arm 13 is mounted directly underthe filaments for heating thereby. In the unheated condition of theswitch arm, electrical connection is made to both the primary andsecondary filaments as seen in dashed line in FIGURE 2 and in theelectric schematic diagram in FIG- URE 5. Thus, initially upon applyingvoltage to the lamp, both filaments will be energized. Switch arm 13will then be heated so as to draw away from the switch contact portion24 of conductor 23- thereby de-energizing the secondary filament butleaving the primary filament energized. The switch arm will be retainedin this laterally displaced position so long as the primary filament isenergized, but is constructed to return automatically to its unheatedposition upon open circulating of the primary filament. When this occursby reason of a failure of the primary filament while voltage is stillapplied, switch arm 13 will return to its unheated position therebyenergizing the secondary filament and to be in turn actuated thereby soas to set up an oscillating pattern of movement causing periodicenergizing and blinking or flashing 3 of the secondary filament 12 whichimmediately informs any observer that the primary filament in the lamphas failed.

A modified form of the invention is illustrated in FIG- URES 6 and 7whereinthe lamp is designedfor special and unusual conditions, such as abank of many lamps operating simultaneously, where the additional powerdrain caused by both filaments operating for a few seconds immediatelyafter the lamps are energized would be undesirable. In this form of theinvention, the primary and secondary filaments 11a and 12a and thethermostatic switch 1311 are connected to input terminals 17a and 18a ina mannercausing initial operation of only the secondary filament 12athen followed by continuous energization of primary filament 11a andde-energizingof filament 12a; the design being so arranged that uponopen circuiting of filament 11a switch 13a will produce periodicenergizing and flashing of filament 12a.

As will be seen from FIGURES 6 and 7 filaments 11a and 12a are eachconnected at one end to input terminal 17. The opposite ends offilaments 11a and 12a are connected to spaced stationarycontacts 31 and32 mounted for engagement with the free swinging end 27a of a bimetalswitch arm of the same type described in connection with the firstembodiment andhaving its opposite end connected to power input terminal18. In the unheated condition of bimetal arm 13a, end 27a will beengaged with contact 31 thus energizing the secondary filament 12a uponapplying voltage to the lamp. Heat generated by the energization offilament 12a will cause arm 13a to swing end 27a away from engagementwith contact 31 and into engagement with contact 32 thus breaking theelectric circuit to the secondary filament and making an electriccircuit with primary filament 11a. Movement of switch arm intoengagement with contact 32 after disengagement from contact 31 andde-energizing of filament 12a will be caused by thermal inertia of the-bi-metal material. Switch arm 13awill remain in engagement with contact32 solong as primary filament 11a embodiment, and re-engages contact 31thereby again energizing secondary filament 12a which inturn heats thebi-metal arm driving it to openthe electrical connection to filament12a, to then cool and return to make electrical contact, thus setting upan oscillating pattern producing periodic energizing andblinking orflashing of filament 12a, thereby furnishinga visual signal of lampfailure.

The most common causes of filament failure in incandescent lamps aresudden surges of overvoltage and aging of filaments due to hours of heatoperation. In the present lamp the secondaryfilament is de-energizedduring normal operation and is not normally subject to sudden voltageincreases since it is only in operation for a few seconds at thebeginning of each use. However,even a sustained overvoltage would onlyresult in a change in the oscillating pattern. The increase in voltagewould cause more heat of the secondary filament and'thereby cause a morerapid movement of. the thermostatic switch resulting in a shorterexposure to the overvoltage. Consequently,

the secondary filament can be relied upon to remain in.

good operating condition until longafter; the primary filament hasfailed.

The flashing rate of the present lamp can be controlled where desirableby four principal factors, viz.,, the type of bi-metal material chosen,the tension of the bi-metal arm, the opposition of thebi-metal arm inrelation to the filaments, and .thefilament voltage. By way of example,the secondary filament mayhave an on time of a fraction of a second, saysomething in the order of second, and a somewhat longer off time, saysomething in the order of 12 second. These times are only indicative andmay, of course, be widely varied to suit the needs or desires of theuser.

As will be also observed, the present lamp may be manufactured at minoradditional cost since the addi tional cost of component materials issmall and the manufacturing techniques are similar to those now used andnot critical.

I claim:

1. An electric lamp comprising, primary and secondary electricallyenergized light emitting elements, a thermostatically operated switchmounted for heating by each of said elements, and for driving thereby toa heated position, said elements and switch being connectedfor normaloperation of'only said primary element, said switch being constructed tomove automatically between said heated position and an unheated positionand being r connected to make and break electrical connection to saidsecondary element in said unheated and heated positions respectively,whereby upon open circuiting of said primary element said switch willproduce periodic energization and blinking of said secondary element.

2. An electric lamp comprising, power input terminals, primary andsecondary filaments each having, one end connected to one of saidterminals, a thermostatically operated switch mounted for heating byeach of said filaments, and driving thereby to a heated position, saidfilaments and switch being connected to the other of said terminals fornormal energizing of only said primary filament, said switch having anormal unheated position making connection to said secondary filamentfor energization thereof and being displaced in said heated positionbreaking said connection, said switch being retained in heated positionso long as said primary filament is energized and being constructed toautomatically return to first position upon open circuiting of saidprimary filament so as to energize said second filament and in turn tobe actuated thereby in an oscillating pattern causing blinking of saidsecondary filament.

3. An electric lamp comprising, power input terminals, a primaryelectrically energized light emitting element connected to saidterminals, a secondary electrically energized light emitting elementconnected to one of said terminals, a thermostatically operated switchconnected to the other of said terminals and being mounted for heatingby each of said elements when energized and having a normal unheatedfirst position making connection to said secondary element forenergization thereof and being driven thereby toa second heated positionbreaking said connection, said switch being constructed to automaticallyreturn to first position upon cooling whereby upon open circuiting ofsaid'primary element said switch will produce periodic energization andblinking of said second element.

4. An electric lamp comprising, primary and secondary electricallyenergized light emitting elements, a thermostatically operatedswitchmounted for heating by each of said elements when energized and beingdriven thereby from a normal unheated position to a spaced heatedposition, said switch being connected to energize said secondary elementin unheated position and to energize said primary element in heatedposition and being constructed toautomatically return to unheatedposition upon cooling.

5. An electric lamp comprising, power input terminals, primary andsecondary filaments each having one end connected to one of saidterminals, a thermostatically operated switch connected to the other ofsaid terminals and being mountedfor heating by each of said filamentswhen energized and being driven thereby from a normal unheated positionto a spaced heated position, said switch being connected to energizesaid secondary filament in said unheated position and being connected toenergize said primary filament in said heated position, said switchbeing retained in heated position so long as said primary filament isenergized and being constructed to automatically return to unheatedposition upon open circuiting of said primary filament so as to energizesaid second 5 6 filament and in turn to be actuated thereby in anoscillating References Cited pattern causing blinking of said secondaryelement.

6. An electric lamp as characterized in claim 5 wherein UNITED STATESPATENTS said switch is composed of an electric current conducting2,448,493 3/1943 M6110 6t 81 X bi-metal arm connected at one end to saidother terminal 5 2,901,667 8/1959 Ketsch et a1. 315-73 X and having anopposite end mounted to swing into electrical contact with said primaryand secondary filaments DAVID J. GALVIN, Primaly Examiner. when said armis heated and cooled respectively,

1. AN ELECTRIC LAMP COMPRISING, PRIMARY AND SECONDARY ELECTRICALLYENERGIZED LIGHT EMITTING ELEMENTS, A THERMOSTATICALLY OPERATED SWITCHMOUNTED FOR HEATING BY EACH OF SAID ELEMENTS, AND FOR DRIVING THEREBY TOA HEATED POSITION, SAID ELEMENTS AND SWITCH BEING CONNECTED FOR NORMALOPERATION OF ONLY SAID PRIMARY ELEMENT, SAID SWITCH BEING CONSTRUCTED TOMOVE AUTOMATICALLY BETWEEN SAID HEATED POSITION AND AN UNHEATED POSITIONAND BEING CONNECTED TO MAKE AND BREAK ELECTRICAL CONNECTION TO SAIDSECONDARY ELEMENT IN SAID UNHEATED AND HEATED POSITIONS RESPECTIVELY,WHEREBY UPON OPEN CIRCUITING OF SAID PRIMARY ELEMENT SAID SWITCH WILLPRODUCE PERIODIC ENERGIZATION AND BLINKING OF SAID SECONDARY ELEMENT.